Method of coating molds and product thereof



Patented Mar. 25, 1941 PATENT" OFFICE METHOD or COATING MOLDS ANDrnonoc'r 'rnnnnor Charles W. Swartout, Kenmore, N. Y., assignor to TheLinde Air Products Company, a. corporation of Ohio No Drawing.Application September 30, 1939, Serial No. 297,363

16 Claims. (01. 22-192) The invention relates to mold coating, and morespecifically to the formation of carbonaceous films on mold surfaces. Itis particularly concerned with improved carbon film coatings for molds,and a new method of applying or depositing such films from a smoky'fiameof acetylene or other hydrocarbon materials.

The need for, and the advantages of, a protective coating over a moldsurface in contact.

with a cast material has long been recognized in the metal and otherarts employing casting and molding processes, and a great variety ofsubstances and compositions have been proposed forthis purpose. Carbonin various forms, either alone or in admixture with other materials, hasbeen of prominent use for mold coating purposes, and deposition ofcarbon films by applying smoky flames of acetylene or other hydrocarbonshas produced very satisfactory results in many industries. The finelydivided soot particles so deposited form a dense and uniform film whichproduces a better finish on the molded article, and the improved heatinsulating characteristics of such coating maintain a better fluid flowof molten material to all parts of the mold, with improvement in thecasting form and detail. These and other. advantages known to the arthave established substantial value and importance in mold coatingsformed by acetylene smoking. I

It is an object of the present invention to provide further improvementsin mold coatings formed by smoking, which will promote and increase thevalue and use of such coatings in the casting art. A further object isto provide improvements in the method of depositing a carbon.

film coating by incomplete combustion of acetylene or other smokeproducing gases, whereby the coating has greater adhesion to the moldsurface with increased permanency and durability. Another object is toimprove the toughness and permanency of the carbon film, therebyeconomically providing a more uniformly satisfactory finish on castingsurfaces.

In accordance with this invention it is proposed to use in conjunctionwith the carbon depositing flame a material adapted to supply anincreased binding action or adhesion of the carbon film to the moldsurface. I have found that the vapors of certain organic liquidsintimately mixed with acetylene or other smoke producing gases, willupon partial combustion in the flame impart to the deposited carbonparticles a greater binding action, productive of a tougher and moredurable coating. Suitable chemicals for this purpose should be ofvolatile nature, or have a fairly high vapor pressure at ordina y roomtemperatures, in order that they may be readily mixed .in vapor phasewith the smoke producing gas. A wide selection of materials is thuspresented which will provide the required binding action when burned ina flame. Of many compounds found suitable by test, certain aldehydes andketones have proven especially effective. Representative of these arecompounds such as octylaldehyde, crotonaldehyde, dicrotonaldehyde anddi-isobutyl ketone.

Acetylene is preferred for producing the sooty deposit and no specialtechnique is required over that shown in the prior art to accomplishsatisfactory smoking. Acetylene burned in the atmosphere froma handtorch or other apparatus under pressures varying from about 3 to 15pounds per square inch, is usually employed for n this purpose, with theflame adjusted so that the luminous part strikes the mold. In thismanner the incandescent carbon particles are chilled and condensed onthe mold surface, forming the carbon deposit without noticeable escapeof smoke into the air. The vapor binding medium may be mixed with, orintimately dispersed in, the acetylene gas in any suitable manner, and aready means of accomplishing this is to conduct the acetylene, in itspassage to the flame, through the volatile liquid binder in a containerhaving a vapor space above the liquid. The acetylene thus becomessaturated with the binder vapor and any entrained liquid can be removedby passing subsequently through a simple trap. With this manner ofdispensing, the actual amount of vapor in the gas-vapor mixture led tothe flame will vary with the vapor pressure of the binding liquidselected, but usually the acetylene will contain not over a maximum ofabout 5% of the chemical vapor, which is suflicient to provide therequired binding action in the deposited carbon films. The resultingcarbon coat is of a toughness and durability impossible to obtain withacetylene alone.

' With but slight variation the process is applicable to provideimprovedcoatings on almost any type of mold, and a wider field of use ofsmoke-formed coatings is indicated by the present invention.Satisfactory coatings can be produced 0n permanen or chill" molds ofeither I metals including lead, aluminum and brass, and in glassmolding, the coating will serveits required function. The vulcanizingand curing of rubber goods, and the molding of plastics are other fieldsin which the invention has substantial merit. By many tests the heatinsulating and mold surface protecting properties of this coating haveproven to be substantially better than the carbon film formed byacetylene alone, and this provides improved casting surfaces,particularly in those of intricate form. The durability and toughness ofthe coating is represented by its ability to withstand several castingoperations, whereas acetylene soot alone often requires renewal aftereach use.

Numerous modifications in the procedure described will be evident tothose skilled in the art. As a binder the vapor of many organic liquidswill be suitable, which have suflicient atmospheric vapor pressure toprovide ready mixing. The binder decomposition to an adhesive residueisattributed above'to a partial combustion, but within these terms anyassociated reactions are intended to be included, as a partialoxidation, polymerization, or some other action also quite probablyoccurs under the conditions of carbon film deposition. Suitable smokingmay be ac complished with gases other than acetylene, and the inventionshould not be limited other than as defined by the appended claims.

I claim:

1. A method of coating molds which comprises intimately mixing with asmoke producing gas a vapor of a compound of the group consistin ofvolatile aldehydes and ketones and applying a carbon deposit to thesurface of the mold with a flame oi said gas-vapor 2. A method ofcoating molds which comprises intimately mixingwith a smoke-producing 8a vapor of the compound octyl-aldehyde, and app y g a carbon deposit tothe surface of the moldwith a flame of said gas-vapor mixture.

3. A method of coating molds which comprises intimately with asmoke-producing gas a vapor of the compound crotonaldehyde, and applyinga carbon deposit to the surface of the mold with a flame of saidgas-vapor mixture.

4. A method of coating molds which comprises intimately mixing with asmoke-producing gas a vapor of the compound di-isobutyl ketone, andapplying a carbon deposit to the surface of the mold with a flame ofsaid gas-vapor mixture.

5. A method of coating molds which comprises intimately mixing withacetylene in an amount less than about 5% a vapor of a compound of thegroup consisting of volatile aldehydes and ketones and applying a carbondeposit to the surface of the mold with a flame of said acetylene-vapormixture.

6. A method of coating molds which comprises intimately mixing withacetylene in an amount less than about 5% a vapor of the compoundoctylaldehyde, and applying a carbon deposit to the surface of the moldwith a flame of said acetylene-vapor mixture.

7. A method of coating molds which comprises intimately mixingwithacetylene in an amount less than ,about 5% a. vapor of the compoundcrotonaldehyde, and applying a carbon deposit to the surface of the moldwith a flame of said acetylene-vapor mixture.

8. A method of coating molds which comprises intimately mixing withacetylene in anamount less than about 5% a vapor of the compounddi-is-obutyl ketone, and applying a carbon deposit to the surface of themold with a flame 5 of said acetylene-vapor mixture.

9. Ina process of coating molds by carbon film deposition from anacetylene flame, the steps which compriseintimately mixing with theacetylen-e a vapor of a compound of the group con- 10 sisting ofvolatile aldehydes and ketones, said vapor being present in about 5% byvolume, and depositing the coating with a flame of said acety-lene-vapormixture.

10. In a process of coating molds by carbon film deposition from anacetylene flame, the steps which comprise intimately mixing with theacetylene about 5% by volume of a vapor of the compound octylaldehyde,and depositing the coating with a flame of said acetylene-vapor'mixture.if)

11. In a process of coating molds by carbon film deposition from anacetylene flame, the steps which comprise intimately mixing with theacetylene about. 5% by volume of a vapor of the compoundci'otonaldehyde, and depositing the 25 coating with a flame of saidacetylene-vapor mixture.

12. In a process of coating molds by carbon film deposition from anacetylene flame, the steps which comprise intimately mixing with theacet- 30 ylene about 5% by volumeof a vapor of the compound di-isobutylketone, and depositing the coating with a flame of said acetylene-vapormixture.

13. A mold having a tough, durable coating 35 thereon, said coatingcomprising a carbon film deposited by a smoke-producing flame ofacetylene, and an adhesive binding said film, said adhesiveconstitutingthe decomposition residue formed by the burning in intimate admixture 4with the acetylene of said smoke-producing flame of a vapor of acompound of the group consisting of volatile aldehydes and ketones.

14. A mold having a tough durable coating thereon, said coatingcomprising a carbon film deposited by a smoke-producing flame of acetyelene, and an adhesive binding said film, said adhesive constituting thedecomposition residue formed by the burning in intimate admixture withthe acetylene of said smoke-producing flame less than 5% by volume of avapor of .the compound octylaldehyde.

15. A mold having a tough durable coating thereon, said coatingcomprising a carbon film deposited by a smoke-producing flame ofacetylene, and an adhesive binding said film, said adhesive constitutingthe decomposition residue formed by the burning in intimate admixturewith the acetylene of said smoke-producing flame less than 5% by volumeof a vapor of the comco pound orotonaldehyde.

16. A mold having a tough durable coating thereon, said coatingcomprising a carbon film deposited by a smoke-producing flame ofacetylene, and an adhesive binding said film, said ad- 5 hesiveconstituting the decomposition residue formed by the burning in intimateadmixture with the acetylene of said smoke-producing flame less than 5%by volume of a vapor or the compound di-isobutyl ketone.

a CHARLES W. SWARTOUT.

